If your cousin has lost the magic, I think Christmas-ish time at DLR is definitely the right time to get the magic back!
You are right - because New Year's Day IS on a stupid Thursday, that means that, inevitably, a lot of folks/parents who would normally be forced back to work the day after New Year's will probably NOT have to go into their offices on January 2 because it is a Friday, and may then hang around DLR at least through Saturday. I had forgotten what days we were talking about. For some reason, I was thinking that the holiday was early in the week like it was last year, but 2008 is a leap year so MAY mess up my theory of everyone heading back to the office the next day.

In fact, I don't know
how I blanked out on that because I was just discussing with my friends the prospect of going back to DLR on December 26 - 29 (not my first choice because of the terrible crowds, but that was the one weekend that people seem to be available), and my friend was saying she didn't think she would be able to take the day off work on the 26th. I reminded her that many offices won't even be open on the 26th because it is sandwiched right between Christmas and the weekend! So I guess the same would apply for the Friday after New Year's too!?!
Anyway, as the PP said, it COULD be crazy busy this holiday season - maybe worse than before - but I still have a hunch that the economy is going to keep a lot of folks away who may have already visited DLR in October. Still, even if it is slightly less crazy than last year, crowds are crowds and you don't want to get stuck in horrible ones!